Tag: bike sharing

Developing a method to score Divvy station connectivity

A Divvy station at Halsted/Roscoe in Boystown, covered in snow after the system was shutdown for the first time to protect workers and members. Photo by Adam Herstein.

In researching for a new Streetsblog Chicago article I’m writing about Divvy, Chicago’s bike-share system, I wanted to know which stations (really, neighborhoods) had the best connectivity. They are nodes in a network and the bike-share network’s quality is based on how well (a measure of time) and how many ways one can move from node to node.

I read Institute for Transportation Development Policy’s (ITDP) report “The Bike-Share Planning Guide” [PDF] says that one station every 300 meters (984 feet) “should be the basis to ensure mostly uniform coverage”. They also say there should be 10 to 16 stations per square kilometer of the coverage area, which has a more qualitative definition. It’s really up to the system designer, but the report says “the coverage area must be large enough to contain a significant set of users’ origins and destinations”. If you make it too small it won’t meaningfully connect places and “the system will have a lower chance of success because its convenience will be compromised”. (I was inspired to research this after reading coverage of the report in Next City by Nancy Scola.)

Since I don’t yet know the coverage area – I lack the city’s planning guide and geodata – I’ll use two datasets to see if Chicago meets the 300 meters/984 feet standard.

Dataset 1

The first dataset I created was a distance matrix in QGIS that measured the straight-line distance between each station and its eight nearest stations. This means I would cover a station in all directions, N, S, E, W, and NW, NE, SE, and SW. Download first dataset, distance matrix.

Each dataset offers multiple ways to gauge connectivity. The first dataset, using a straight-line distance method, gives me mean, standard deviation, maximum value, and minimum value. I sorted the dataset by mean. A station with the lowest mean has the greatest number of nearby stations; in other words, most of its nearby stations are closer to it than the next station in the list.

Sorting the first dataset by lowest mean gives these top five best-connected stations:

  1. Canal St & Monroe St, a block north of Union Station (191), mean of 903.96 feet among nearest 8 stations
  2. Clinton St & Madison St, outside Presidential Towers and across from Northwestern Train Station (77), 964.19 feet
  3. Canal St & Madison St, outside Northwestern Train Station (174), 972.40
  4. Canal St & Adams St, north side of Union Station’s Great Hall (192), 982.02
  5. State St & Randolph St, outside Walgreens and across from Block 37 (44), 1,04.19

The least-connected stations are:

  1. Prairie Ave & Garfield Blvd (204), where the nearest station is 4,521 feet away (straight-line distance), or 8.8x greater than the best-connected station, and the mean of the nearest 8 stations is 6,366.82 feet (straight-line distance)
  2. California Ave & 21st St (348), 6,255.32
  3. Kedzie Ave & Milwaukee Ave (260), 5,575.30
  4. Ellis Ave & 58th St (328), 5,198.72
  5. Shore Drive & 55th St (247), 5,168.26

Dataset 2

The second dataset I manipulated is based on Alex Soble’s DivvyBrags Chrome extension that uses a distance matrix created by Nick Bennett (here’s the file) that estimates the bicycle route distance between each station and every other station. This means 88,341 rows! Download second dataset, distance by bike – I loaded it into MySQL to use its maths function, but you could probably use python or R.

The two datasets had some overlap (in bold), but only when finding the stations with the lowest connectivity. In the second dataset, using the estimated bicycle route distance, ranking by the number of stations within 2.5 miles, or the distance one can bike in 30 minutes (the fee-free period) at 12 MPH average, the following are the top five best-connected stations:

  1. Ogden Ave & Chicago Ave, 133 stations within 2.5 miles
  2. Green St & Milwaukee Ave, 131
  3. Desplaines St & Kinzie St, 129
  4. (tied) Larrabee St & Kingsbury St and Carpenter St & Huron St, 128
  5. (tied) Clinton St & Lake St and Green St & Randolph St, 125

Notice that none of these stations overlap with the best-connected stations and none are downtown. And the least-connected stations (these stations have the fewest nearby stations) are:

  1. Shore Drive & 55th St, 11 stations within 2.5 miles
  2. (tied) Ellis Ave & 58th St and Lake Park Ave & 56th St, 12
  3. (tied) Kimbark Ave & 53rd St and Blackstone Ave & Hyde Park Blvd and Woodlawn Ave & 55th St, 13
  4. Prairie Ave & Garfield Blvd, 14
  5. Cottage Grove Ave & 51st St, 15

This, the second dataset, gives you a lot more options on devising a complex or weighted scoring system. For example, you could weight certain factors slightly higher than the number of stations accessible within 2.5 miles. Or you could multiply or divide some factors to obtain a different score.

I tried another method on the second dataset – ranking by average instead of nearby station quantity – and came up with a completely different “highest connectivity” list. Stations that appeared in the least-connected stations list showed up as having the lowest average distance from that station to every other station that was 2.5 miles or closer. Here’s that list:

  1. Kimbark Ave & 53rd St – 13 stations within 2.5 miles, 1,961.46 meters average distance to those 13 stations
    Blackstone Ave & Hyde Park Blvd – 13 stations, 2,009.31 meters average
    Woodlawn Ave & 55th St – 13 stations, 2,027.54 meters average
  2. Cottage Grove Ave & 51st St – 15 stations, 2,087.73 meters average
  3. State St & Kinzie St – 101 stations, 2,181.64 meters average
  4. Clark St & Randolph St – 111 stations, 2,195.10 meters average
  5. State St & Wacker Dr – 97 stations, 2,207.10 meters average

Back to 300 meters

The original question was to see if there’s a Divvy station every 300 meters (or 500 meters in outlying areas and areas of lower demand). Nope. Only 34 of 300 stations, 11.3%, have a nearby station no more than 300 meters away. 183 stations have a nearby station no further than 500 meters – 61.0%. (You can duplicate these findings by looking at the second dataset.)

Concluding thoughts

ITDP’s bike-share planning guide says that “residential population density is often used as a proxy to identify those places where there will be greater demand”. Job density and the cluster of amenities should also be used, but for the purposes of my analysis, residential density is an easy datum to grab.

It appears that stations in Woodlawn, Washington Park, and Hyde Park west of the Metra Electric line fare the worst in station connectivity. The 60637 ZIP code (representing those neighborhoods) contains half of the least-connected stations and has a residential density of 10,468.9 people per square mile while 60642, containing 3 of the 7 best-connected stations, has a residential density of 11,025.3 people per square mile. There’s a small difference in density but an enormous difference in station connectivity.

However, I haven’t looked at the number of stations per square mile (again, I don’t know the originally planned coverage area), nor the rise or drop in residential density in adjacent ZIP codes.

There are myriad other factors to consider, as well, including – according to ITDP’s report – current bike mode share, transit and bikeway networks, and major attractions. It recommends using these to create a “demand profile”.

Station density is important for user convenience, “to ensure users can bike and park anywhere” in the coverage area, and to increase market penetration (the number of people who will use the bike-share system). When Divvy and the Chicago Department of Transportation add 175 stations this year – some for infill and others to expand the coverage area – they should explore the areas around and between the stations that were ranked with the lowest connectivity to decrease the average distance to its nearby stations and to increase the number of stations within 2.5 miles (the 12 MPH average, 30-minute riding distance).

N.B. I was going to make a map, but I didn’t feel like spending more time combining the datasets (I needed to get the geographic data from one dataset to the other in order to create a symbolized map). 

Citibike in New York City differs slightly from Chicago’s Divvy

I visited New York City two weekends ago for a Streetsblog writers conference. I was there for three nights and four days. To get around I put a bunch of cash on a Metrocard to use the subway and JFK Airtrain and I bought a 7-day pass for the Citibike bike-share system.

Citibike and Divvy in Chicago use nearly identical equipment from the same manufacturer, and Alta Bicycle Sharing operates both systems. Citibike sells the 7-day pass for $25, a relative steal for personal transportation costs in New York City – probably any city. Divvy only offers 24-hour and annual passes.

Citibike stations have maps of a better design that matches the walking wayfinding stanchions that New York City’s Department of Transportation has installed. The stations integrate the ad+map board onto the kiosk while Divvy has separated them. I don’t see an operational advantage to either design, but there does seem to be less material used in Citibike’s integrated design which uses one fewer solar panel.

I’ve never used Divvy’s touch-screen kiosk to obtain a single ride code as part of using a day pass so I can’t compare it to interacting with the Citibike kiosk to obtain the ten or so ride codes I needed on my trip. This was the most infuriating part of the experience, which annual members don’t experience because they have a key: the kiosk is very slow in responding to a tap and sometimes the docking bay wouldn’t accept my brand new ride code. You can’t get a replacement ride code for two minutes, preventing quick dock surfing.

The bicycles seem exactly the same: too small of a gear ratio which means a slow top speed and an easy-to-reach “over pedaling” threshold. This may be more important for New York City to have because you must climb 140 feet up the bridges to cross between Manhattan and Brooklyn or Queens while Chicago has no significant slopes. I eventually stopped using Citibike in favor of the subway and walking. I like riding trains almost as much as I like riding a bicycle and cycling in downtown Manhattan is difficult if you’re unsure of a good route to get to your destination. I prefer to not use an app for directions because of how frequently the turns appear meaning I have to inspect the app just as often to ensure I made the right one.

I’d like to see my Divvy key work in other cities where Alta operates bike-sharing. Just charge my bank card on file, applying the lowest-cost pass and letting me bypass the user agreements before purchasing a pass in another city.

That wasn’t a joyride on Lake Shore Drive

Video starts at Ohio Street (you can see the W Hotel after the curve at Ontario Street); the camera holder and driver speak with expletives.

Craig Newman at the Sun Times is wrong about the person in this video, who was filmed riding a Divvy bike-share bike along the jersey barrier on northbound Lake Shore Drive. He blogged today:

All excellent questions. But let’s maybe simplify and throw a warning sticker on the bikes: NO RIDING ON EXPRESSWAYS

And yes, I am a consistent bike commuter who enjoys the benefits and routinely laments stupidity, four-wheeled, two-wheeled and on foot we all have to fight through daily. But come on. Lake Shore Drive?

This person didn’t want to be cycling there. There are several ways one could make the mistake of riding a bike on this roadway. And once you’re on, you’re on for good until the next exit (which in this Divvy rider’s case is 1/4 mile north from where the video was shot).

She might have known there was something called the Lake Shore Path (as some people call it) or the Lakefront Trail – she couldn’t remember which. She didn’t see any “Route X” signs, or “Interstate Y” signs.

She saw a road that looks like so many others. It’s called a drive, not an expressway (it doesn’t meet those technical standards). She most likely entered from Lower Wacker (which connects to Michigan Avenue, where many people ride Divvy against Alderman Reilly’s desire) and went up the center, northbound ramp to Lake Shore Drive.

Stony Island Avenue in Chicago. The only difference between this and Lake Shore Drive is the more frequent stopping (unless there’s congestion on LSD) and the shopping. Photo by Jeff Zoline.

It can be easily mistaken for a typical road, looking similar to the stroads near wherever she lives. Like Stony Island, Cicero, Columbus, Archer, in Chicago, or any countless “major street” in the suburbs. Maybe she comes from Roscoe Village, where Western Avenue goes over Belmont, or Bridgeport/Brighton Park, where Ashland Avenue goes over Pershing Avenue. Or some other city where regular roads cross other regular roads at different grades.


View Larger Map

Local photographer Brent Knepper tweeted that he made the mistake before.

We have a problem with our design such that the highway didn’t sufficient communicate, “No really, you shouldn’t bike here”. On the contrary, we have roads that should be shouting, “Hey, you really should be biking here!”

Maybe that’s why Netherlands makes it perfectly clear with red pavement.

Believe me, not even Casey Neistat would ride up here intentionally.

Updated with a better guess of where she entered Lake Shore Drive.

How to convert bike-share JSON data to CSV and then to shapefile

Update January 4, 2013: The easiest way to do this is to use Ian Dees’s Divvy API as it outputs straight to GeoJSON (which QGIS likes). See below.

For Michael Carney’s Divvy bike-share stations + Census tract + unbanked Chicagoans analysis and map he needed the Divvy station locations as a shapefile. I copied the JSON-formatted text of the Divvy real-time station API, converted it to CSV with OpenRefine, and then created a shapefile with QGIS.

Here’s how to create a shapefile of any bike-share system that uses hardware from Public Bike System Co based on Montréal and is operated by Alta Bicycle Share (this includes New York City, Chattanooga, Bay Area, Melbourne, and Chicago): Continue reading

Divvy considers my suggestions in bike-share kiosk map redesign

The new design that will appear at the newest stations first and then rolled out to all stations. 

I posted two months ago a critique of the Divvy bike-share maps, seen at 284 stations scattered around Chicago, focusing on the clutter of having so many maps (with the third being useless), unclear labels and labels that covered map objects, and the low prominence of the smartphone app and map legend. Two weeks ago the Divvy public relations manager emailed me a screenshot of the new map design and said that these points had been changed. He said they considered four of my suggestions:

  1. Make CycleFinder, the official Divvy smartphone app, more prominent
  2. Change “You are here” design to make it clear where you are
  3. Make streets and streets’ label text smaller
  4. Removed service area map and make legend more prominent

I replied to the manager and suggested that the “You are here” label be made slightly transparent to show that the road does continue beneath it.

Close-up of the original “you are here” design that covered up other objects and wasn’t centered in the walking distance circle.